Remote transport of material is an utmost useful, but challenging, property expanding the design possibilities of many applications such as microfluidics or robotics where species can be carried without interfering with its environment. Nature has solved the problem of transport in e.g., the respiratory system by a concerted motion of cilia. This study addresses a new method to fabricate an array of small parallel fibers acting as cilia placed side by side on a substrate. The fibers consist of a crosslinked liquid crystal main chain polymer functionalized with coreactant azobenzene molecules. The fibers bend toward a light source in a concerted manner. When placed in a liquid, the cooperative bending motion of the fibers creates a flow able to efficiently carry objects. The proposed fabrication process of the fibers is scalable to large area and requires an optimized rheology which is achieved by converting low molecular weight reactive liquid crystal acrylate monomers to oligomers using a multiplication of the monomeric units by the Michael addition reaction with dithiol. The oligomer properties and the elasticity of the fibers are adjusted by changing the thiol spacer leading to optimized manufacturing and maximized optical response.

Stimuli-responsive materials based on interpenetrating liquid crystal-hydrogel polymer networks are fabricated. These materials consist of a cholesteric liquid crystalline network that reflects color and an interwoven poly(acrylic acid) network that provides a humidity and pH response. The volume change in the cross-linked hydrogel polymer results in a dimensional alteration in the cholesteric network as well, which, in turn, leads to a color change yielding a dual-responsive photonic material. Furthermore a patterned coating having responsive and static interpenetrating polymer network areas is produced that changes both its surface topography and color.

This work describes the fabrication, characterization, and modelling of liquid crystalline polymer network films with a multiple patterned 3D nematic director profile, a stimuli-responsive material that exhibits complex mechanical actuation under change of temperature or pH. These films have a discrete alternating striped or checkerboard director profile in the plane, and a 90-degree twist through the depth of the film. When actuated via heating, the striped films deform into accordion-like folds, while the film patterned with a checkerboard microstructure buckles out-of-plane. Furthermore, striped films are fabricated so that they also deform into an accordion shaped fold, by a change of pH in an aqueous environment. Three-dimensional finite element simulations and elasticity analysis provide insight into the dependence of shape evolution on director microstructure and the sample's aspect ratio.

An efficient and selective porous nanostructured polymer adsorbent is prepared from smectic liquid crystals. The adsorption study is performed by using hydrophilic dyes as water pollutants. The anionic pore interior of the nanoporous polymer is able to selectively adsorb cationic methylene blue over anionic methyl orange. Even zwitter ionic rhodamine B could hardly be adsorbed due to the presence of the anionic group in this dye. The confined pore dimensions allow size selective adsorption; a 4^th generation cationic dendrimer is not able to diffuse into the nanometer sized pores. The porous nature of the polymer provides easy and fast accessibility of all adsorption sites. Stoichiometric ion exchange is obtained, which equates to an adsorption capacity of nearly 1 gram of methylene blue per 1 gram adsorbent. A competitive Langmuir adsorption constant and pseudo second order rate constant are determined. The adsorbent and adsorbate could both be retrieved after acid treatment of the polymer.

Chiral-nematic polymer network coatings form a “fingerprint” texture through self-assembly. For this purpose the molecular helix of the coating is oriented parallel to the substrate. The coating has a flat surface but when actuated by light in the presence of a copolymerized azobenzene compound, 3D fingerprint structures appear in the coating. The helix forms protrusions at the positions where the molecules are aligned parallel to the surface and withdraws at the positions where the orientation is perpendicular. This process proceeds rapidly and is reversible, that is, the fingerprint-shaped protrusions disappear when the light is switched off. The texture in the on-state resembles that of a human fingerprint and is used to manipulate the gripping friction of a robotic finger. The friction coefficient drops by a factor of four to five when the fingerprint switched on because of reduced surface contacts.

Chiral-nematic polymer network coatings form a “fingerprint” texture through self-assembly. For this purpose the molecular helix of the coating is oriented parallel to the substrate. The coating has a flat surface but when actuated by light in the presence of a copolymerized azobenzene compound, 3D fingerprint structures appear in the coating. The helix forms protrusions at the positions where the molecules are aligned parallel to the surface and withdraws at the positions where the orientation is perpendicular. This process proceeds rapidly and is reversible, that is, the fingerprint-shaped protrusions disappear when the light is switched off. The texture in the on-state resembles that of a human fingerprint and is used to manipulate the gripping friction of a robotic finger. The friction coefficient drops by a factor of four to five when the fingerprint switched on because of reduced surface contacts.

Herein, we describe the preparation of patterned photoresponsive hydrogels by using a facile method. This polymer-network hydrogel coating consists of N-isopropylacrylamide (NIPAAM), cross-linking agent tripropylene glycol diacrylate (TPGDA), and a new photochromic spiropyran monoacrylate. In a pre-study, a linear NIPAAM copolymer (without TPGDA) that contained the spiropyran dye was synthesised, which showed relatively fast photoswitching behaviour. Subsequently, the photopolymerisation of a similar monomer mixture that included TPGDA afforded freestanding hydrogel polymer networks. The light-induced isomerisation of protonated merocyanine into neutral spiropyran under slightly acidic conditions resulted in macroscopic changes in the hydrophilicity of the entire polymer film, that is, shrinkage of the hydrogel. The degree of shrinkage could be controlled by changing the chemical composition of the acrylate mixture. After these pre-studies, a hydrogel film with spatially modulated cross-link density was fabricated through polymerisation-induced diffusion, by using a patterned photomask. The resulting smooth patterned hydrogel coating swelled in slightly acidic media and the swelling was higher in the regions with lower cross-linking densities, thus yielding a corrugated surface. Upon exposure to visible light, the surface topography flattened again, thus showing that a hydrogel coating could be created, the topography of which could be controlled by light irradiation.

Hydrogen-bridged, cholesteric liquid-crystal (CLC) polymer networks are adopted as an optical sensor material to distinguish between ethanol and methanol. Fast uptake of the alcohols is facilitated by an incorporated porosity created by breaking the hydrogen bridges and by a previously removed non-reactive liquid-crystal agent. The discrimination between the alcohols is based on the diversity in molecular affinity of ethanol and methanol with the hydrogen-bridged CLC polymer networks. The CLC networks are molecular-helix-based, one-dimensional bandgap materials with a discrete reflection band in the visible part of the spectrum that depends on the pitch of the molecular helix. The changes in positions of the reflection bands of the CLC network accurately discriminate between the alcohol types and provide information on their ratio in case they are blended.